A planetary gear unit, also called a planetary gear set, in general consists of a planet carrier (planetary gear carrier), a planet pin (planetary gear pin) mounted in the planetary carrier, as well as planets (planetary gears) which are mounted on the planet pins. The planetary carrier may be constructed from a forming part with angled arms and a guide disc or from two parallel guiding washers which are connected to one another via rivet bolts. A planet carrier of this type has been known from EP 1 214 536 B1 by the applicant, whereby the rivet bolts are peened with the guide discs. The guide discs are manufactured as fine-blanking parts and have perforations into which rivet bolt journals arranged on the end side are inserted and subsequently peened. When securing the journal the knife edge rings engage, on the one hand, with the guide disc from the tool side and, on the other hand, from the rivet bolt side, and thus prevent the material from giving way.
Fine-blanking is a known method which has been defined by K. Lange, Umformtechnik, Vol. 3, Metal sheet working, Springer 1990, p. 152 ff. as follows: “Fine-blanking refers to the cutting out and perforation process of work pieces made of flat metal products with specifically modified stress conditions in the shearing zone without fissures on the cut surface used as functional surface by means of a blanking die, blanking stamps, blank holders and ejectors”. Immediately before blanking, a knife edge ring is pressed into the work piece (metal sheet) at a small distance from the cutting line, as a result of which compression stresses are superimposed in the shear zone. The final outcome will be a smooth and fissure-free cut surface.
From EP 1 266 154 B1 by the applicant a method has been known for an accurately positioned assembly of a planetary gear unit, whereby the planet pins are peened with the guide discs in a similar manner as the above mentioned rivet bolts. The planet pins have shoulders and journals on the end side which are inserted with a radial clearance into the perforations of the guide discs. The journals are then peened and the radial gap filled by the material of the journal that has been displaced outward. The material of the guide discs is clamped in the area of the perforations by the meshing knife edge rings.
Another method for the accurately positioned assembly of a planetary gear unit has been known from DE 10 2004 057 576 A1 by the applicant, whereby the planet pins are centered and aligned opposite to the guide discs prior to being peened. The planet pins have open lengthwise bores on the end side with which conical tips of opposed dies mesh and thus achieve an alignment.
The problem with the known methods for the assembly of a planetary gear unit is the exact centering and alignment of the planet pin such that optimal meshing of the teeth of the planetary gears with the corresponding sun and ring gear is ensured. Potential solutions still result nonetheless.